Migration of PIPELINED from Oracle to Postgres - sql

Question

Creation of TYPE is as follows:
create or replace Type T_dates as OBJECT(
p_st_date VARCHAR2(32767),
p_en_date VARCHAR2(32767)
);
create or replace TYPE T_dates_tab AS table of T_dates;
Sample Code which needs to convert is as follows.
Oracle Code:
Function f_get_dates(p_st_date varchar2,
p_end_date varchar2,
p_st_time varchar2,
p_end_time varchar2)
return T_dates_tab PIPELINED
IS
V_DAY_COUNT NUMBER;
P_TEMP_ST_DATE VARCHAR2(100 ):=p_st_date;
BEGIN
SELECT TO_DATE(p_end_date,'MM-DD-YYYY ') - TO_DATE(p_temp_st_date,'MM-DD-YYYY ') INTO V_DAY_COUNT FROM DUAL ;
WHILE V_DAY_COUNT >= 0
LOOP
DBMS_OUTPUT.PUT_LINE(p_temp_st_date||' '||p_st_time||','||p_temp_st_date||' '||p_end_time);
PIPE ROW (T_dates((p_temp_st_date||' '||p_st_time),(p_temp_st_date||' '||p_end_time)));
SELECT TO_CHAR(TO_DATE(p_temp_st_date,'MM-DD-YYYY')+1,'MM/DD/YYYY') INTO p_temp_st_date FROM DUAL;
SELECT TO_DATE(p_end_date,'MM-DD-YYYY ') - TO_DATE(p_temp_st_date,'MM-DD-YYYY ') INTO V_DAY_COUNT FROM DUAL ;
END LOOP;
DBMS_OUTPUT.PUT_LINE('f_get_dates');
RETURN;
END f_get_dates;
Need Postgres Inputs for the above Oracle code.

Answer 1

This function can be massively simplified in Postgres. In fact you don't really need your own function for that:
select p_st_date::date + time '00:00:00' as p_st_date,
p_st_date::date + time '18:00:00' as p_en_date
from generate_series(date '2018-01-01', date '2018-01-30', interval '1' day) as t(p_st_date);
In contrast to your function this returns real timestamp values rather than character values. If you indeed want to treat timestamp values as character data, use to_char() to convert that.
You can put the above into a SQL function:
create function f_get_dates(p_st_date date, p_en_date date, p_st_time time, p_end_time time)
returns table (p_st_date timestamp, p_en_date timestamp)
as
$$
select p_st_date::date + p_st_time as p_st_date,
p_st_date::date + p_end_time as p_en_date
from generate_series(p_st_date, p_en_date, interval '1' day) as t(p_st_date);
$$
language sql;
If you really want to return the timestamps as character values, just format them using to_char():
create function f_get_dates(p_st_date date, p_en_date date, p_st_time time, p_end_time time)
returns table (p_st_date varchar, p_en_date varchar)
as
$$
select to_char(p_st_date::date + p_st_time, 'mm-dd-yyyy hh24:mi:ss') as p_st_date,
to_char(p_st_date::date + p_end_time, 'mm-dd-yyyy hh24:mi:ss') as p_en_date
from generate_series(p_st_date, p_en_date, interval '1' day) as t(p_st_date);
$$
language sql;